Exposure to Secondhand Marijuana Smoke Can Be Just as Dangerous as Cigarette Smoke

Being exposed to secondhand marijuana smoke may be just as dangerous as being exposed to secondhand cigarette smoke, says a new study by researchers from the University of California-San Francisco.

For the study, the researchers exposed laboratory rats to secondhand marijuana smoke using a modified cigarette smoking machine. The team then used a high-resolution ultrasound machine to measure the rats’ blood vessel function ten minutes before exposure and then 40 minutes after exposure. After being exposed to the smoke for a half hour, the blood vessel function of the rats reduced by 70 percent.

The team then exposed the rats to secondhand smoke from marijuana that did not contain THC. They found that a half hour of exposure to this smoke also reduced the rats’ blood vessel function, indicating that the effect is not related to THC.

As a comparison, the researchers assessed the effects of secondhand exposure to THC-free marijuana and plain air. Rats experiences no change in blood vessel function when exposed to the air.

The researchers note that secondhand exposure to tobacco smoke is known to reduce blood vessel function, but this effect usually wears off within 40 minutes. However, in this study, the blood vessel function of rats exposed to secondhand marijuana smoke had not returned to normal after 40 minutes.

The research team said that these results are worrisome, since impaired blood vessel function can increase the risk of heart attack and heart disease.

“Most people know secondhand cigarette smoke is bad for you,” said senior author Matthew Springer, an associate professor of medicine in the Department of Cardiology at UCLA. “But many don’t realize that secondhand marijuana smoke may also be harmful.”

With more and more states legalizing marijuana for recreational use, Springer added that the effects of exposure to secondhand marijuana smoke is an increasing public health concern.

“If you’re hanging out in a room where people are smoking a lot of marijuana, you may be harming your blood vessels,” he said. “There’s no reason to think marijuana smoke is better than tobacco smoke. Avoid them both.”